Artifacts with radeon 9500 (r300), opensource drivers and compiz

Hi,

I have an ATI radeon 9500 and I would like to use the open-source drivers to run compiz. But when I enable the desktop effects I get an screen full off artifacts, but the speed is fine. I played some games en don't see any artifact while playing them. Is compiz not supported with the open-source drivers or is something else wrong?

This is an screen shot of the artifacts, it's a little old but is shows the exact same problem.
http://members.home.nl/gotiniens/weblog/images/r300artifacts.png

output of glxinfo:
gotiniens@gotiniens-desktop:~$ glxinfo
name of display: :0.0
display: :0 screen: 0
direct rendering: Yes
server glx vendor string: SGI
server glx version string: 1.2
server glx extensions:
    GLX_ARB_multisample, GLX_EXT_import_context, GLX_EXT_texture_from_pixmap,
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_copy_sub_buffer,
    GLX_OML_swap_method, GLX_SGI_make_current_read, GLX_SGI_swap_control,
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_visual_select_group
client glx vendor string: SGI
client glx version string: 1.4
client glx extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context,
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_allocate_memory,
    GLX_MESA_copy_sub_buffer, GLX_MESA_swap_control,
    GLX_MESA_swap_frame_usage, GLX_OML_swap_method, GLX_OML_sync_control,
    GLX_SGI_make_current_read, GLX_SGI_swap_control, GLX_SGI_video_sync,
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer,
    GLX_SGIX_visual_select_group, GLX_EXT_texture_from_pixmap
GLX version: 1.2
GLX extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context,
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_copy_sub_buffer,
    GLX_MESA_swap_control, GLX_MESA_swap_frame_usage, GLX_OML_swap_method,
    GLX_SGI_make_current_read, GLX_SGI_swap_control, GLX_SGI_video_sync,
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_visual_select_group
OpenGL vendor string: DRI R300 Project
OpenGL renderer string: Mesa DRI R300 20060815 AGP 8x x86/MMX+/3DNow!+/SSE TCL
OpenGL version string: 1.3 Mesa 7.0.1
OpenGL extensions:
    GL_ARB_fragment_program, GL_ARB_imaging, GL_ARB_multisample,
    GL_ARB_multitexture, GL_ARB_texture_border_clamp,
    GL_ARB_texture_compression, GL_ARB_texture_cube_map,
    GL_ARB_texture_env_add, GL_ARB_texture_env_combine,
    GL_ARB_texture_env_crossbar, GL_ARB_texture_env_dot3,
    GL_MESAX_texture_float, GL_ARB_texture_mirrored_repeat,
    GL_ARB_texture_rectangle, GL_ARB_transpose_matrix,
    GL_ARB_vertex_buffer_object, GL_ARB_vertex_program, GL_ARB_window_pos,
    GL_EXT_abgr, GL_EXT_bgra, GL_EXT_blend_color,
    GL_EXT_blend_equation_separate, GL_EXT_blend_func_separate,
    GL_EXT_blend_minmax, GL_EXT_blend_subtract, GL_EXT_clip_volume_hint,
    GL_EXT_compiled_vertex_array, GL_EXT_convolution, GL_EXT_copy_texture,
    GL_EXT_draw_range_elements, GL_EXT_gpu_program_parameters,
    GL_EXT_histogram, GL_EXT_packed_pixels, GL_EXT_polygon_offset,
    GL_EXT_rescale_normal, GL_EXT_secondary_color,
    GL_EXT_separate_specular_color, GL_EXT_stencil_two_side,
    GL_EXT_stencil_wrap, GL_EXT_subtexture, GL_EXT_texture, GL_EXT_texture3D,
    GL_EXT_texture_edge_clamp, GL_EXT_texture_env_add,
    GL_EXT_texture_env_combine, GL_EXT_texture_env_dot3,
    GL_EXT_texture_filter_anisotropic, GL_EXT_texture_lod_bias,
    GL_EXT_texture_mirror_clamp, GL_EXT_texture_object,
    GL_EXT_texture_rectangle, GL_EXT_vertex_array, GL_APPLE_packed_pixels,
    GL_ATI_blend_equation_separate, GL_ATI_texture_env_combine3,
    GL_ATI_texture_mirror_once, GL_IBM_rasterpos_clip,
    GL_IBM_texture_mirrored_repeat, GL_INGR_blend_func_separate,
    GL_MESA_pack_invert, GL_MESA_ycbcr_texture, GL_MESA_window_pos,
    GL_NV_blend_square, GL_NV_light_max_exponent, GL_NV_texture_rectangle,
    GL_NV_texgen_reflection, GL_NV_vertex_program, GL_OES_read_format,
    GL_SGI_color_matrix, GL_SGI_color_table, GL_SGIS_generate_mipmap,
    GL_SGIS_texture_border_clamp, GL_SGIS_texture_edge_clamp,
    GL_SGIS_texture_lod

   visual x bf lv rg d st colorbuffer ax dp st accumbuffer ms cav
 id dep cl sp sz l ci b ro r g b a bf th cl r g b a ns b eat
----------------------------------------------------------------------
0x23 24 tc 0 32 0 r y . 8 8 8 8 0 24 8 0 0 0 0 0 0 None
0x24 24 tc 0 32 0 r y . 8 8 8 8 0 24 0 0 0 0 0 0 0 None
0x25 24 tc 0 32 0 r y . 8 8 8 8 0 24 8 16 16 16 16 0 0 Slow
0x26 24 tc 0 32 0 r y . 8 8 8 8 0 24 0 16 16 16 16 0 0 Slow
0x27 24 tc 0 32 0 r . . 8 8 8 8 0 24 8 0 0 0 0 0 0 None
0x28 24 tc 0 32 0 r . . 8 8 8 8 0 24 0 0 0 0 0 0 0 None
0x29 24 tc 0 32 0 r . . 8 8 8 8 0 24 8 16 16 16 16 0 0 Slow
0x2a 24 tc 0 32 0 r . . 8 8 8 8 0 24 0 16 16 16 16 0 0 Slow
0x2b 24 dc 0 32 0 r y . 8 8 8 8 0 24 8 0 0 0 0 0 0 None
0x2c 24 dc 0 32 0 r y . 8 8 8 8 0 24 0 0 0 0 0 0 0 None
0x2d 24 dc 0 32 0 r y . 8 8 8 8 0 24 8 16 16 16 16 0 0 Slow
0x2e 24 dc 0 32 0 r y . 8 8 8 8 0 24 0 16 16 16 16 0 0 Slow
0x2f 24 dc 0 32 0 r . . 8 8 8 8 0 24 8 0 0 0 0 0 0 None
0x30 24 dc 0 32 0 r . . 8 8 8 8 0 24 0 0 0 0 0 0 0 None
0x31 24 dc 0 32 0 r . . 8 8 8 8 0 24 8 16 16 16 16 0 0 Slow
0x32 24 dc 0 32 0 r . . 8 8 8 8 0 24 0 16 16 16 16 0 0 Slow
0x63 32 tc 0 32 0 r . . 8 8 8 8 0 0 0 0 0 0 0 0 0 Ncon